Labour today called on Prime Minister David Cameron to disclose all his communications with former News International executive Rebekah Brooks amid claims that a tranche of e-mails and text messages between them was not handed over to the Leveson Inquiry.
The demand came after Cameron refused to answer a question about the messages in the House of Commons.
In a letter to the PM, shadow culture secretary Harriet Harman said it was "vital" that Lord Justice Leveson's inquiry into media standards had all the evidence available, and called on Cameron to hand over all his communications with Brooks and former News of the World editor Andy Coulson.
The Independent reported earlier this week that dozens of e-mails had not been released to Lord Justice Leveson as part of his inquiry, which was prompted by allegations of phone-hacking at the News of the World. But Downing Street insisted that it had handed over all the material requested from it.
Cameron's official spokesman told reporters today: "We have given the Leveson Inquiry the information that they wanted, the relevant information."
But Harman told the PM in her letter: "In order for the public to have total confidence it would be preferable for you to disclose all of the e-mails and let the Leveson Inquiry decide which are relevant."
The Labour deputy leader later said: "The reports that the Prime Minister has not made a full disclosure to the Leveson Inquiry are deeply concerning.
"The Prime Minister set up the Leveson Inquiry to examine the culture, practices and ethics of the press including the relationships between the press and politicians. It presents an historic opportunity to solve long-standing problems with the press and it is therefore vital that the Leveson Inquiry has all of the evidence available.
"In order for the public to have total confidence, David Cameron should disclose all of his communications with Rebekah Brooks and all of his communications with Andy Coulson and let the Leveson Inquiry decide which are relevant. I have therefore written to the Prime Minister urging him to do that."
Brooks resigned as chief executive of News International over the phone-hacking scandal last year, while Mr Coulson quit as director of communications at 10 Downing Street.
Labour MP Chris Bryant – himself a victim of phone-hacking – asked Mr Cameron at Prime Minister's Questions today: "Why won't you publish all the texts, e-mails and forms of correspondence between yourself and your office, and Rebekah Brooks, Andy Coulson and News International so we can judge whether they are relevant?
"Is it because they are too salacious and embarrassing for you, or is it because there is one rule for the Prime Minister and another for the rest of us?"
Cameron replied: "Before answering this question, I would like everyone to recall you stood up in this House and read out a whole lot of Leveson information which was under embargo and you were not meant to read out, much of which turned out, about me, to be untrue, and you have never apologised.
"Until you apologise, I'm not going to answer your questions."
After the session, a senior Labour source said: "Saying 'I'm not going to answer a question' is not acceptable. It is the Prime Minister's job to answer questions in Prime Minister's Question Time – the clue is in the name.
"He does have a duty to answer questions. It would be nice if he did it for once."
Asked whether Cameron was within his rights to refuse to answer Bryant's questions, the PM's official spokesman said: "He can give the answer he likes. They choose the questions, he chooses the answers."